Apparatus for the production of extinguishing foam



APPARATUS FOR THE PRODUCTION OF EXTINGUISi-IING FOAM Filed Oct. 30, 1951Sept. 4, 1956 v. VASSILKOVSKY 2 Sheets-Sheet 1 Int/e 722 b 7 loiakmryajs ilko us/iig/ p 4, 1956 v. VASSILKOVSKY 2,761,516

APPARATUS FOR THE. PRODUCTION OF EXTINGUISHING FOAM Filed OGE. 3Q, 19512 Sheets-Sheet 2 fray 6712 07"; A PZZZDZdfkiSiZ/ZOZ/Jg United StatesAPPARATUS FOR THE PRODUCTION OF EX'IINGUISHING FQAM The presentinvention relates to apparatus for the production of fire extinguishingair foam, such apparatus comprising a mixing tube provided at one endwith injector means fed with a foam forming liquid under pressure andwith means for admitting air into said mixing tube arranged adjacent tothe injector means, the foam forming liquid being either an aqueoussolution of an emulsifying agent or a separate emulsifying agent whichis mixed with water in the mixing tube.

Prior art apparatus for the production of this air foam have been basedon the assumption that, to obtain a stable foam, in other words a veryfine emulsion of the foam forming liquid and air, it is required to veryfinely divide, up to a spray condition, the jet of said liquid whenentering the mixing tube in which it is mixed with air. Prior artapparatus built on this principle include therefore either a number offine water jets which are parallel to or cross one another; or arevolving jet, the rotary motion of which is obtained through obliqueguiding blades; or several jets, approximately parallel, offering somedispersion to give rise to a turbulent flow when said dispersion bringsthem into contact. Nevertheless, this more or less accentuated divisionof the liquid into jets or the imparting of rotary motion to the liquidwill result in an important loss of energy, with the result that theseapparatus, when used like a waterhose nozzle for direct projection in tothe open air will not have an adequate range or, if they are connectedwith a flexible ror rigid piping having a hose nozzle at its dischargeend will not allow a discharge of the foam to an adequate height anddistance.

The object of the present invention is the production of a finer andmore stable foam than that obtained in the known extinguishing air-foamdevices.

A further object of the invention is to increase the distance and/ orthe height over which the air-foam might be conveyed under its ownpressure.

Still another object of the invention is to provide in the mixing tube aturbulent flow of the emulsion formed by the foam forming liquid and theair, without the necessity of finely dividing the liquid as it isinjected into the mixing tube.

A further object of the invention is to provide a turbulent fiow of thefoam over a path forming an important fraction of the total length ofthe mixing tube.

With these objects in view, the apparatus according to the inventioncomprises a single slightly divergent in jector nozzle arrangedcoaxially at the inlet end of the mixing tube, whereby a singledivergent central jet having a density substantially uniformlydistributed over its cross-section is obtained causing the cross section:of the mixing tube to be entirely filled with a compact flow of a largebubble primary foam, at a point distant from the discharge end of saidtube.

The inventor has ascertained that, if a turbulent flow is propitious tothe formation of a fine foam, it is not absolutely necessary to rely onrotation or on spraying to very finely divide the jet of liquid underpressure; when atent 2,761,516 Patented Sept. 4, 1956 the liquid jet,driving along the air andforming large bubbles which can be calledprimary foam entirely fills the cross sectional area of the pipe, theprimary foam will flow in a full jet and as the Reynolds number for themixture of the aqueous solution of the emulsifying gent with the air, isvery much greater than the limit number, the flow will not be laminarbut turbulent; in this connection, it is advisable to point out that,for the known apparatus above mentioned in which a rotary motion isimparted to the liquid jet entering the mixing tube, favorableconditions are not created for the formation of a primary foam inasmuchas the rotary motion gives rise to a hollow divergent jet, the liquidbeing distributed in the form of a conical sheet.

In a similar manner, turbulent flow facilitating the formation of stablefoam is not obtained in devices of another known type wherein theinjector means are arranged to produce a hollow cylindrical or taperedjet by means of an annular injecting nozzle fed with the foam formingliquid.

The length of the pipe, starting from the cross section which isentirely filled by the primary foam is about eight times its diameter.To obtain an adequate proportion of air and of liquid (from six to ninevolumes of air to one volume of liquid), corresponding to a foam of goodquality, the total cross section of the pipe should be about seven toten times greater than the area of the nozzle port of the single centraljet of liquid: this port may have a diameter as large as desired,according to the output required from the apparatus, and for instancemay be 25 mm. and even greater. In the case of a cylindrical jet, thetotal length of the pipe should be equal to from 20 to 60 times itsdiameter, said length being possibly reduced in a marked way when adivergent nozzle is used, as this kind of nozzle brings the sectionwhere the primary-foam entirely fills the pipe nearer to the inlet endof said pipe.

Other means to reduce the total length of the pipe and which can also beused simultaneously with a divergent nozzle consists in enlarging thecross sectional area of the pipe along that portion of the pipe in whichthe said portion is completely filled by the liquid jet, said enlargedcross-sectional portion of the pipe being preferably connected with afirst portion which has a smaller diameter, through a tapered tubeportion, to avoid energy losses resulting from a sudden change in crosssection. Because of the speed decrease of the foam which accumulates inthe enlarged portion, its loss of kinetic energy results in increasedpressure; this pressure increase reacts back on the primary-foamcontained in the portion having a smaller diameter resulting in that thesection starting from which the primary-foam entirely fills the crosssection of the pipe, is brought nearer to the inlet end of the pipe.Thus the total length of the pipe may be reduced accordingly. Theenlarged portion of the pipe may be connected either with a flexiblepiping, or provided with a convergent nozzle to be used like a waterhose nozzle.

By roughening the inner wall of the pipe, the setting up of notationalmovement of the liquid jet is reduced and thus the length of the pipemay be further reduced.

By way of example, several embodiments of the apparatus of the presentinvention are described hereafter and illustrated in the accompanyingdrawings.

Figure 1 shows an axial section of an apparatus including a cylindricalnozzle and a pipe having a constant cross section.

Figure 2 is an axial section of another embodiment having a divergentnozzle.

Figure 3 shows an apparatus including a cylindrical nozzle and a pipeincluding an enlarged portion.

Figure 4 shows an axial section of an apparatus includ- 3 ing adivergent nozzle and also a pipe ending in an enlarged portion.

Figure shows on an enlarged scale an axial section of a pipe equippedwith a divergent nozzle and a cross section of the conical jet thusproduced.

Figure 6 shows an axial section of an alternative embodiment of thedevice used to inject the water and the emulsifyng agent.

Figure 7 shows the outlet end of a pipe used like a hose nozzle.

Figure 8 shows the connection of the apparatus with a flexible deliveryhose. 7

Figure 9 is an axial section of another alternate embodiment of theinjecting device.

As shown in Figure 1, the apparatus includes a cylindrical pipe 1 havinga constant cross section and a total length of at least 20 times itsdiameter. This pipe is fed at one end through a single centralcylindrical nozzle 2 which injects into the pipe an aqueous solution ofthe foam generating agent, the air being sucked by the central, jet 3through the annular opening 4 surrounding the nozzle. This central jetforms, in the first portion of its flow,

' an emulsion having large bubbles (above designated as primary foam),which starts at the section designated as A to entirely fill the crosssectional area of the pipe 1. The total length of the pipe is so chosenthat the remaining portion, from A to B will permit the. turbulent flowarising in said portion to change the primary foam into a fine andstable emulsion which will be ejected into the open air at the end B inthe shape of a powerful and far reaching jet. in the embodiment ofFigure 2, the nozzle 2 is slightly divergent and the section A in thepipe 1 at which the primary foam 5 will entirely fill the cross sectionof the pipe, is nearer to the injector with. the result that, as thelength of the second portion, A to B of. the. pipe remains unchanged,the total length of the pipe is reduced. As shown in Figure 5, thedivergent jet 5, contrary to what happens in the case of a rotary jet,is not hollow and forms a conical beam constituted by a great number ofthin jets, more or less evenly distributed through the cross-section ofthe jet, as shown at 5' in the cross sectional view at the right inFigure 5. In the said Figure 5, the air is sucked into the pipe 1through two series of staggered ports 6 and 6 arranged near the inlet ofthe pipe in two circular rows. I p

In order to shorten the overall length of the delivery tube theapparatus according to the invention shown in Figure 3, comprising apipe 1, with a cylindrical nozzle 2, is provided in the second portionAto B in which the flow starts to be turbulent, with a chamber 7, havinga larger diameter and ending, when the foam is to. be ejected directlyin the open air, in a convergent nozzle. For the. above mentionedreasons, the pressure increase in the enlarged chamber results inbringing nearer to the. pipe inlet the section A in which the sectionalarea of the pipe is entirely filled by the primary foam, so that thetotal length can be reduced approximately to the same value as for thepipe bearing a divergent nozzle of Figure 2.

In Figure 4, the means used in Figures 2 and 3 are combined and theapparatus includes both a divergent nozzle 2, and an enlarged chamber 7,thus allowing even more of the total length of the pipe to be reducedwith the benefit of an important decrease of the bulkiness and theweight of the apparatus. To reduce energy losses, the portions 1 and 7of the pipe having various diameters are connected, as shown in Figure4, through a conical portion 9 thereby obtaining a gradual and slowincrease of the cross sectional area so that the foaming jet will notbreak away from contact with the wall of the pipe.

Of course, instead of injecting an aqueous solution of the foamproducing agent into the pipe of the apparatus, it is possible toproduce the solution within the apparatus itself, as shown in Figure 6:the foam producing agent is sucked through the central nozzle 10 bywater injected through the annular opening between the. nozzles 10 and11, the nozzle 11 being cylindrical or divergent as desired, and the airbeing sucked, as in Figure 5, through the rows of ports 3, 3'. It isalso possible, as in Figure 9, to inject the Water through a centraldivergent nozzle 12, to introduce the emulsifying agent through thepiping 15 and through an annular opening 13 formed between the cen tralnozzle 12 and a concentric ring 14, whilst the air is sucked through thewide mouthed piping 16.

As shown in Figures 7 and 8, the end 8 of the pipe 1 may be equippedwith a threaded tip 17 on which is screwed, as shown in Figure 7, aconvergent nozzle 18 to eject the foam directly into the open air by along range jet, or the connection 19 and a flexible hose 20 allowing thefoam to be conveyed over a rather large distance and height.

What I claim is:

1. In an apparatus for the production of air-foam a mixing tubecomprising a first cylindrical portion provided at one of its ends withinjector means for introducing a foam forming liquid into said tube,said means comprising a single slightly divergent nozzle arrangedcoaxially with said tube and adapted to produce a single centraldivergent jet having a density substantially uniformly distributed overits cross section and causing the cross section of said first part ofthe mixing tube to be entirely filled before its discharge end, saidmixing tube further comprising a second tapered portion connected to thefirst cylindrical portion and having progressively increasing diameter,and a third enlarged cylindrical terminal portion connected to saidtapered portion.

2. In an apparatus for the production of air-foam a mixing tubecomprising a first cylindrical portion provided at one of its ends withinjector means for introducing a foam forming liquid into said tube,said means comprissection of said first part of the mixing tube to beentirely filled before its discharge end, said mixing tube furthercomprising a second tapered portion connected to the first cylindricalportion and having progressively increasing diameter, and a thirdenlarged cylindrical terminal portion connected to said tapered portionand provided at its discharge end with. a convergent nozzle.

3. In an apparatus for the production of air-foam a mixing tubecomprising a. first cylindrical portion provided at one of its ends withinjector means. for introducing a foam forming. liquid into said. tube,said means comprising a single slightly divergent nozzle arrangedcoaxially with said tube and adapted to produce a single centraldivergent jet having a density substantially uniformly distributed overits cross. section and causing the cross section of said first part ofthe mixing tube to be entirely filled before its discharge end, the saidcylindrical portion having a cross section of about seven. to ten timesgreater than the area of the outlet of the divergent nozzle, and alength at most equal to twelve times the diameter thereof, said mixingtube further comprising a second tapered portion connected to the firstcylindrical portion and having a progressively increasing diameter, anda third enlarged cylindrical terminal portion connected to said taperedportion, the total length of the tapered portion and of the enlargedcylindrical terminal portion being approximately equalto eight times thediameter of the first cylindrical. portion of the mixing tube 4. In anapparatus for the production of air-foam a mixing tube comprising afirst cylindrical portion provided at one of its ends with injectormeans for introducing a foam forming liquid into saidtube, said meanscomprising a single slightly divergent nozzle arranged coaxially withsaid tube and adapted to produce a single central divergent jet having adensity substantially uniformly distributed' over its cross section andcausing the cross section of said first part of the mixing tube to beentirely filled before its discharge end, the said cylindrical portionhaving a cross section of about seven to ten times greater than the areaof the outlet of the divergent nozzle, and a length at most equal totwelve times the diameter thereof, said mixing tube further comprising asecond tapered portion connected to the first cylindrical portion andhaving a progressively increasing diameter, and a. third enlargedcylindrical terminal portion connected to said tapered portion, thetotal length of the tapered portion and of the enlarged cylindricalterminal portion being approximately equal to eight times the diameterof the first cylindrical portion of the mixng tube, a convergent nozzleprovided at the discharge end of the enlarged terminal portion of themixing tube.

References Cited in the file of this patent UNITED STATES PATENTS

